The present invention relates to rotating control buttons, of the type used for example in watches and commonly called time-setting crowns. It concerns more particularly a button including a metal body, of generally cylindrical shape, and provided with a blind hole intended to accommodate a control stem.
Such buttons, made of metal, are well known to those skilled in the art. They are fitted to most watches provided with hands. They allow time-setting, and winding for mechanical watches. The user must thus be able to pull out the button to select a function and rotate it in order to modify a value.
In order to facilitate the rotation of the button, the latter may most often include grooves on the cylindrical portion of its external surface. Unfortunately such grooves are abrasive, tend to wear out clothes, and do not always allow a good grip in particular as regards traction.
It is well known that organic materials, such as rubber, allow greater adherence than metal, without however causing wear. These materials are, however, too lacking in rigidity to be able to be the only constituent material of a control button.
In order to have a control button having, during use, the advantages of metal and rubber, it seems natural to coat the grooves with a synthetic material. This solution has numerous drawbacks. The metal surface has to be pre-treated to allow a synthetic material to adhere thereto, said treatment having to be adapted to each type of material; it is very difficult to delimit very precisely the covered zones so that it is very often necessary to do a finishing machining operation such as polishing; since the thickness of synthetic material deposited is very small the coating is liable to wear and accidental tearing.
The present invention mainly concerns a button made of two metal/synthetic materials so that it does not have the drawbacks of the aforecited prior art.
The invention thus concerns a control button having a metal body 10, 52 provided along its axis Axe2x80x94A with a blind hole 16, 58 closed by a cap 18 extended by a wall 14 of revolution, said button including on all or part of the exterior of its wall 14 a gripping zone made of synthetic material, characterised in that body 10, 52 of the button includes an annular groove 20, 62 made in the outer surface of its wall 14, 56 in proximity to the opening of blind hole 16, 58 and channels 26 connecting said outer surface of wall 14 and the bottom of blind hole 16, 58, and in that a fitting 12 made of synthetic material 12 is made in situ to form a ring 22, 64 housed in groove 20, 62 and whose raised portions 34 extend along axis Axe2x80x94A over the outer surface of wall 14, 56 at least as far as the openings of channels 26, a radial structure with several branches 30 closing said channels 26 and a core 32 connecting said branches 30 to secure between them the different parts of fitting 12.
Consequently, the fitting forms on the exterior of the body portions in relief which facilitate gripping, and on the interior loops, each of them gripping the metal body, which allows the best possible fastening conditions.
In order to facilitate the driving in rotation of the control button, the portions of the synthetic fitting in relief define raised portions connecting the ring to the branches, or an annular ring provided with grooves.
In certain applications, for example when the button according to the invention is used as the time-setting crown of a watch, it is subjected to traction efforts. If this effort is exerted frequently on the synthetic material, this may result in premature wear, able to cause it to be torn off. This is why it is advantageous for the necessary effort to be applied to the metal body. For this purpose, the latter has a ring defining the side of the groove in proximity to the opening of the blind hole.
For the aforementioned application, the crown is often required to participate in the water-resistant sealing of the watch. Generally, the interior of the cylindrical wall is provided with an O-ring gasket co-operating with a part of the case to close, in a water-resistant manner, the opening through which the control means of the watch pass. This O-ring gasket slides into a housing in the crown.
Another object of the present invention is to make a control button wherein the gripping fitting made of synthetic material also forms a sealing gasket. Therefore, and in another particular embodiment, the button according to the invention is characterised in that its fitting extending through additional channels inside the blind hole has an O-ring structure attached to the inner wall of the blind hole to form a sealing gasket.